Filter assembly having a flexible housing and method of making same

ABSTRACT

A fluid filter assembly for filtering fluids such as blood is described. The assembly includes first and second filter housing elements formed by an injection molding process. Each element is flexible and includes a peripheral flange formed thereabout and a fluid communicating port formed therein. Filter media, such as a filter membrane, is sealed between the mating flanges of two elements. The fluid filter assembly is capable of collapsing and expanding during the filtration process depending upon the composition of the fluid passed there through. A method for making the filter assembly and systems for using the filter assembly are also disclosed.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.10/055,862 filed Jan. 23, 2002, now U.S. Pat. No. 6,601,710, which is acontinuation of U.S. patent application Ser. No. 09/295,048, filed Apr.20, 1999, abandoned, which is a continuation-in-part of U.S. patentapplication Ser. No. 08/697,270 filed Aug. 21, 1996, (now U.S. Pat. No.6,032,807), which is a continuation of U.S. patent application Ser. No.08/558,458, filed Nov. 16, 1995, abandoned, which is a continuation ofU.S. patent application Ser. No. 08/392,297, filed Feb. 22, 1995,abandoned, which is a continuation of U.S. patent application Ser. No.08/173,608, filed Dec. 22, 1993, abandoned.

FIELD OF THE INVENTION

The present invention relates to an improved filter device forfiltering, entrapping air, and preventing foaming in fluids, such asbiological matter, including whole blood or blood components. Morespecifically, the invention relates to a filter assembly having aninjection molded filter housing and a method of making a filter housingfor performing the same. The invention may be used in blood collectionand processing systems for removing leukocytes from whole blood, redblood cells, plasma, and platelets prior to transfusion or long termstorage.

BACKGROUND OF THE INVENTION

It is common in the formation of medical and laboratory filters, such asblood filters or blood filtration housings containing filters, to formfilter housings for filter media from one or more sheets of flexiblepolyvinyl chloride (PVC) material. It is also common to manufacturefilter housings from rigid plastics such as acrylic, polypropylene, or asimilar material.

Many types of devices are commercially available for separating wholeblood components. Some machines are fully automated while others rely onmanual operations performed by technicians. On a gross level, bloodcomponents include plasma (water and protein), red blood cells,leukocytes, and platelets. Filter media is commercially available tofilter leukocytes from blood. A filter pad media for filteringleukocytes from blood cells is disclosed in U.S. Pat. No. 5,591,337,commonly owned by the assignee hereof.

While filter housings manufactured from flexible PVC material offer thebenefit of having a flexible housing, it has been heretofore difficultto provide an efficient and reliable method for forming an inlet portand an outlet port in the filter housing. Prior art filter housings madefrom one or more sheets of PVC material have taught the formation of theport along the peripheral seal of the respective PVC material sheetedges. Typically, a short piece of tubing is used as the port. See, forexample, U.S. Pat. No. 4,035,304 to Watanabe issued Jul. 12, 1977 andentitled Blood Filtering Bag. However, it is difficult to form acomplete and reliable seal at the junction of the PVC material sheetsand the tubing that serves as the port. Both an incomplete seal, as wellas a weak seal can lead to fluid leaking from the filter assembly duringthe filtering process.

Introducing fluid into a filter housing at the seal of its panels orsheets is also less desirable when the flow characteristics of the fluidacross the filter media are important (e.g. laminar flow or even flowacross the filter media). If the fluid enters the housing immediatelyadjacent the filter media, the bubble strength of the filter media maybe quickly surpassed by increased blockage of the filter media withfiltered particulate and the resulting increased pressure within thefilter housing may cause the filter media to rupture or burst. This is avery undesirable result in that it is difficult, if not impossible toimmediately detect a ruptured filter membrane. Alternatively, increasedblockage of the filter media may lead to turbulent fluid flow throughthe filter assembly. Many fluids react poorly to turbulent flow.

A similar prior art filter is taught in published European PatentPublication No. 0 516 846 to Sakamoto published Dec. 9, 1992 andentitled Bag-Like Filter. This application teaches the formation offilter housings from heat-fusible polyethylene films. In one embodimentthe inlet and outlet ports are formed from polyethylene tubing fusedbetween the film and the filter at their edges. Alternatively, separateinlet and outlet ports having a construction similar to a valve placedin a tire tube may be fused through an opening formed in the centralregions of the film sheets.

Other prior art devices, such as U.S. Pat. No. 5,507,904, commonly ownedby the assignee hereof, teach the formation of the inlet and outletports in the wall of a thermoplastic sheet filter housing by firstforming a slit in the filter housing wall, inserting a separate tubethrough the slit and heating the mating materials to fuse the tube andsheet. While providing a very reliable filter assembly, extra care mustbe taken during the manufacturing process to ensure that the slit is nottoo large, the tube is properly placed prior to heating, and a good sealis formed around the tubing-wall junction. Some prior art filterassemblies do not include positive stops for the conduits attached totheir filter ports. Without a stop, the possibility exists that therubber or plastic conduit may be inserted too far into the port, therebypossibly damaging or piercing the filter media. In addition, if solventis used to bond the conduit to the port, the solvent may contact andthereby degrade the filter media.

Filter housings molded from hard plastics such as acrylic allow for theformation of the inlet and outlet ports at almost any location along thewall or panel of the filter housing. The location is primarily limitedonly by the sophistication of the mold or die. However, the resultingfilter assemblies have the drawback that they are not flexible and thuscannot substantially prevent a phenomenon common in fluid filteringprocesses known as “foaming.” It is also sometimes necessary tocentrifuge a blood container having a filter device attached thereto. Ahard plastic filter housing may puncture or damage the blood containerduring the centrifuge process.

Most of the whole blood collected from donors today is not itself storedand used for transfusion. Instead, the whole blood is separated into itsclinically proven components (typically red blood cells, platelets, andplasma), which are themselves individually stored and used to treat amultiplicity of specific conditions and diseased states. For example,the red blood cell component is used to treat anemia; the concentratedplatelet component is used to control thrombocytopenic bleeding; and theplatelet-poor plasma component is used as a volume expander or as asource of Clotting Factor VIII for the treatment of hemophilia.

Automated centrifugal blood collection systems and manual systemscomposed of multiple, interconnected plastic bags have met widespreaduse and acceptance in the collection, processing and storage of theseblood components. In the United States, these systems are subject toregulation by the government. For example, the plastic materials fromwhich the bags and tubing are made must be approved by the government.In addition, the maximum storage periods for the blood componentscollected in these systems are prescribed by regulation.

In the United States, whole blood components collected in a non-sterile,or “open”, system (e.g. one that is open to communication with theatmosphere) must, under governmental regulations, be transfused withintwenty-four hours. However, when whole blood components are collected ina sterile, or “closed”, system (e.g., one that is closed tocommunication with the atmosphere), the red blood cells can be stored upto forty-two days (depending upon the type of anticoagulant and storagemedium used); the platelet concentrate can be stored up to five days(depending upon the type of storage container); and the platelet-poorplasma may be frozen and stored for even longer periods. Conventionalsystems of multiple, interconnected plastic bags have met withwidespread acceptance, because these systems can reliably provide thedesired sterile, “closed” environment for blood collection andprocessing, thereby assuring the maximum available storage periods.

In collecting whole blood components for transfusion, it is desirable tominimize the presence of impurities or other materials that may causeundesired side effects in the recipient. For example, because ofpossible febrile reactions, it is generally considered desirable totransfuse red blood cells substantially free of the white blood cellcomponents, particularly for recipients who undergo frequenttransfusions.

One way to remove leukocytes is by washing the red blood cells withsaline. This technique is time consuming and inefficient, as it canreduce the number of red blood cells available for transfusion. Thewashing process also exposes the red blood cells to communication withthe atmosphere, and thereby constitutes a “non-sterile” entry into thestorage system. Once a non-sterile entry is made in a previously closedsystem, the system is considered “opened”, and transfusion must occurwithin twenty-four hours, regardless of the manner in which the bloodwas collected and processed in the first place. In the United States, anentry into a blood collection system that presents the probability ofnon-sterility that exceeds one in a million is generally considered toconstitute a “non-sterile” entry.

Another way to remove leukocytes is by filtration. Systems and methodsfor accomplishing this within the context of conventional multiple bloodbag configurations are described in Wisdom U.S. Pat. Nos. 4,596,657 and4,767,541, as well as in Carmen et al U.S. Pat. Nos. 4,810,378 and4,855,063. In these arrangements, an inline leukocyte filtration deviceis used. The filtration can thereby be accomplished in a closed system.However, the filtration processes associated with these arrangementsrequire the extra step of wetting the filtration device before use witha red blood cell additive solution or the like. This added stepcomplicates the filtration process and increases the processing time.

Other systems and methods for removing leukocytes in the context ofclosed, multiple blood bag configurations are described in Stewart U.S.Pat. No. 4,997,577. In these filtration systems and methods, a transferassembly dedicated solely to the removal of leukocytes is used. Thetransfer assembly is attached to a primary blood collection container.The transfer assembly has a transfer container and a first fluid pathleading to the transfer container that includes an inline device forseparating leukocytes from red blood cells. The transfer assembly alsohas a second fluid path that bypasses the separation device. Using thesesystems and methods, leukocytes are removed as the red blood cells areconveyed to the transfer container through the first fluid path. The redblood cells, now substantially free of leukocytes, are then conveyedfrom the transfer container back to the primary collection container forstorage through the second fluid path, this time bypassing theseparation device.

A need still exists for an improved biological matter filter housingthat is flexible and that includes an inlet or an outlet port integrallyformed in the housing. A need exists for an improved filter housingcapable of trapping air and preventing foaming of the fluid or bloodpassed through the filter. A need also exists for a form of a fluidfilter having an inlet and an outlet formed tangentially in a flexiblewall of the filter assembly. A need exits for an improved flexiblefilter housing having integral ports including positive stops forconduits connected to the filter also exists. Because these types ofdevices are often used only once (e.g. disposable) a need exists for anefficient, reliable and low cost method of making the filter assembly.

SUMMARY OF THE INVENTION

It is a principle object of the present invention to provide an improvedfilter device having a body defined by at least one injection molded,flexible filter housing element sealed to form an interior chamber. Afilter medium is located within the chamber. The housing element has atleast one port integrally molded therein. The integrally formed portsare tangential or substantially tangential to the filter housing wallsand parallel to the filter medium.

In one embodiment, a filter device is provided and defined by at leastone injection molded housing element having a flexible portion formedtherein and sealed along edges thereof to form an interior cavity. Afilter membrane is sealed within the cavity. At least one port, in fluidcommunication with the interior cavity, is integrally molded in theflexible portion. In a specific application, the port is positionedtangentially with respect to the flexible portion and the filter deviceis positioned horizontally with respect to the port.

In another embodiment the filter device comprises first and secondgenerally flexible injection molded filter housing elements, eachelement having a flange formed about a periphery thereof and a domedportion formed therein. At least one port is molded in the domedportion. The filter housing elements arranged along their respectiveflanges to form an interior cavity and a filter membrane, having anouter periphery, is positioned between the filter housing elements. Thefirst filter housing element flange, the filter membrane outer peripheryand said second filter housing element flange are sealed together toform an interior cavity. Each port is in fluid communication with theinterior cavity.

In another embodiment, the invention includes a container comprising aninjection molded sheet having a substantially flexible portionintegrally molded therein. The sheet is sealed along an edge afterinjection molding forming an interior chamber and at least one port isintegrally formed in the flexible portion of the sheet. The port is influid communication with the interior chamber.

In yet further embodiments, a blood processing system is disclosedincluding a first bags, a second bag, and tubing providing communicationbetween the two bags and including a blood filter or device of a typedescribed above.

For example, the invention may be utilized in a multiple container bloodcollection system for conveniently processing the various components ofblood. In such a system, the filter device of the present inventionperforms the function of separating the undesired matter, e.g.,leukocytes, during processing. The system is arranged so that some bloodcomponents can be conveyed through the filter device, while othercomponents can be readily conveyed along other paths that bypass thefilter device.

An important aspect of the invention is that the filter housing elementor elements are flexible thus allowing the filter device to expand andcontract during the filtration process. In a preferred embodiment, thefilter housing elements are dome-like in structure and the inlet oroutlet port is molded in a central region of the dome. Due to itsflexible structure, the filter device is capable of minimizing foamingof the fluid passed therethrough. The volume of the interior chamber iscapable of increasing and decreasing its volume during the filtrationprocess. While the filter medium is initially spaced a predetermineddistance from the housing element, this distance may also change duringthe filtration process.

Another important aspect of the invention is that the filter device iscapable of trapping air while in a horizontal orientation. In thisorientation, the inlet port is positioned on the upper surface of thedevice and the outlet port is positioned on the lower surface.Accordingly, the present invention is well suited for applications onhorizontal planes (e.g. the top panel of an instrument).

Yet another important aspect of the invention is that each filterelement is injection molded thus producing a unitary, single filterelement including a flexible portion and an integrally molded fluidport. The fluid ports include a port opening extending from the exteriorof the element, through its flexible portion and into the elementinterior. The filter device inlet and outlet ports may include structurefor limiting the insertion of a conduit therein. In a preferredembodiment, the filter elements may be molded from a thermoplasticmaterial, such as polyvinyl chloride.

The filter media or medium enclosed within the filter device may be anyof a great number of known filtration materials. As one example, thefilter medium may comprise a polyester mesh material. In a specificapplication of the filter device, the filtration material is may beselected to remove undesirable materials, such as leukocytes, from wholeblood, red blood cells, platelet rich plasma, platelet poor plasma orplatelet concentrate. Examples of these filtration materials can befound in the following patents: U.S. Pat. Nos. 5,591,337, 5,089,146,4,767,541, 5,399,268, 5,100,564, 4,330,410, 4,701,267, 4,246,107,4,936,998 and 4,985,153. Each of these patents is incorporated herein byreference.

In accordance with a related aspect, the possibility of damaging orpiercing the filter medium is eliminated by the inclusion of structurewithin the port opening that forms a stop. This aspect is particularlyimportant when it is desirable to connect a conduit to the filterassembly using only an interference fit between the conduit and the portopening.

The first and second filter housings may be identical to one another. Inthis manner, the orientation of the filter ports can be readilypositioned during the manufacturing process in the same direction or inopposed directions, depending upon the fluid to be passed through thefilter, the filter medium and/or the location and applicationconstraints of the filter device.

In accordance with an important specific application of the invention,the filter device may be incorporated into an apparatus for collectingand separating the various components of whole blood, e.g. red bloodcells, platelets and blood plasma. The apparatus may be an automatedblood separation apparatus or manual apparatus.

In accordance with another aspect of the invention, an injection moldingdie is provided to mold from a thermoplastic material filter housingelements, each having a flange portion, a flexible central region and anintegral port. A second pair of opposed dies is provided to seal filtermedia between first and second filter housing elements. The dies, whichare formed of an electrically conductive material are positioned so thatthe first housing element, filter media, and a second housing elementare placed between said dies. When RF energy is transmitted to theflange portions of the first and second filter housings through theconductive dies, the thermoplastic material is caused to soften or meltand to flow to seal the periphery of the filter media between thehousing elements.

In a preferred method of forming the fluid filter device from athermoplastic material, the method comprises the steps of injectionmolding first and second flexible filter housings, each housing having aport integrally formed therein and having a periphery thereabout;placing a filter membrane between said first and second filter housingperipheries; and sealing along the periphery of the filter housing toform a fluid tight enclosure. In addition, the resulting enclosure maybe trimmed in a cutting die to produce a more aesthetically pleasingfilter device.

The fusing or sealing step may be conducted by placing the metallic dieson opposite sides of the filter housings and applying energy to theperipheries to dielectrically heat said peripheries to cause softeningand sealing thereof. Alternatively, the fusing or sealing step may beconducted by the application of radio frequency energy.

Multiple filter housing elements may be molded and multiple filterhousing assemblies may be formed at the same time. Utilizing this methoda third cutting die is provided to individually cut each completedfilter assembly from a carrier web.

Further advantages and aspects of the invention will be apparent fromthe following detailed description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the filter assembly;

FIG. 2 is a top plan view of the filter assembly;

FIG. 3 is a bottom plan view of the filter assembly;

FIG. 4 is a right side elevation view of the filter assembly, the leftside elevation view being a mirror image thereof;

FIG. 5 is a front elevation view of the filter assembly;

FIG. 6 is a cross sectional view taken along line 6—6 in FIG. 2 showingthe filter media within the filter assembly;

FIG. 7 is a perspective view of the filter assembly connected to inletand outlet fluid conduits;

FIG. 8 is a top plan view of multiple filter housing bodies connected bya web;

FIG. 9 is a front elevation view showing the multiple filter housingbodies being formed by an upper die and a lower die;

FIG. 10 is an exploded perspective view of the filter housings andfilter media prior to assembly;

FIG. 11 is a perspective view of the filter housings and filter mediaprior to assembly;

FIG. 12 is an exploded perspective view of the filter assemblies afterthe heating step;

FIG. 13 is an exploded perspective view of the filter assemblies afterthe die cutting step;

FIG. 14 is a perspective view of a second embodiment of the filterassembly;

FIG. 15 is a top plan view of the filter assembly shown in FIG. 14;

FIG. 16 is a bottom plan view of the filter assembly shown in FIG. 14;

FIG. 17 is a right side elevation view of the filter assembly of thefilter assembly shown in FIG. 14, the left side elevation view being amirror image thereof;

FIG. 18 is a front elevation view of the filter assembly shown in FIG.14;

FIG. 19 is a cross sectional view taken along line 19—19 in FIG. 15showing the filter media within the filter assembly;

FIG. 20 is a schematic view of a red blood cell collection systemincluding the present invention;

FIG. 21 is a schematic view of the system shown in FIG. 20 being used totransfer platelet-rich component to an associated transfer assembly;

FIG. 22 is a schematic view of the system shown in FIG. 20 being used totransfer an additive solution from the associated transfer assembly intothe red blood cells in the primary collection container;

FIG. 23 is a schematic view of the system shown in FIG. 20 being used toremove undesired matter from the red blood cells in another transferassembly, while platelet and plasma separation occurs in the nowseparated first transfer assembly;

FIG. 24 is a schematic view of the system shown in FIG. 20 with all theassociated storage containers separated for the storage of individualcomponents;

FIG. 25 is a schematic view of an additional filtering step utilizingthe system shown in FIG. 20 being used to remove undesired matter fromthe platelet concentrate;

FIG. 26 is a schematic view of an alternative arrangement of the systemshown in FIG. 20, in which the various assemblies comprise initiallyseparate subassemblies that are joined together at time of use;

FIG. 27 is a schematic view of a white blood cell collection systemincluding the present invention;

FIG. 28 is a schematic view of the system shown in FIG. 27 being used totransfer whole blood to an associated transfer assembly;

FIG. 29 is a schematic view of the system shown in FIG. 27 being used totransfer an additive solution from the associated transfer assembly intothe red blood cells in the primary collection container;

FIG. 30 is a schematic view of the system shown in FIG. 27 being used totransfer red blood cells into a transfer assembly; and

FIG. 31 is a schematic view of the system shown in FIG. 27 with all theassociated storage containers separated for the storage of individualcomponents.

DETAILED DESCRIPTION

Although the disclosure hereof is detailed and exact to enable thoseskilled in the art to practice the invention, the physical embodimentsherein disclosed merely exemplify the invention which may be embodied inother specific structure. While the preferred embodiment has beendescribed, the details may be changed without departing from theinvention, which is defined by the claims.

Referring more particularly to the drawings there is seen in FIG. 7 afilter assembly 10 used, for purposes of illustration only, to filterblood or blood components, e.g., red blood cells or platelet poor plasmain a manual or automated blood processing system during processing orbefore being returned to a donor from a blood separation apparatus. Twoor more conduits, such as conduits 50 and 52 supply unfiltered blood toand convey filtered blood from the filter assembly 10 respectively.Filter media, not shown in FIG. 7, is contained within filter assembly10. Blood filtration is only one application of the invention and is notintended to be a limitation of the present invention. Numerous otherapplications of the invention will be apparent to those skilled in theart.

Referring now to FIGS. 1 through 5, the preferred embodiment of filterassembly 10 can be seen to include first and second filter housingelements 20 and 22. As will hereinafter be appreciated, and as isapparent from FIGS. 2 and 3, the housing elements 20 and 22 areidentical. Each housing element 20 and 22 includes a flange 24 formedabout its periphery 26. A domed region 30 is formed within the flangearea 24. The filter housing elements 20 and 22 are arranged, as will bedescribed in greater detail, so that their domed regions 30 form anddefine an interior filter cavity 32.

The domed region 30 of each filter housing element 20 or 22 has at leastone port 40 formed integral with the filter housing element. Port 40includes an inlet 42 that passes though domed region 30 and that is influid communication with the interior cavity 32 of the filter assembly10. Inlet 42 is sized to receive the end of a fluid carrying conduit,such as a flexible medical grade plastic (e.g., PVC) or rubber tube orhose. As best shown in FIG. 4, a shoulder 44 is formed within each inlet42 to act as a conduit stop. The conduit stop prevents the insertion ofconduit 50 or 52 too far into the filter assembly thereby possiblydamaging or rupturing the filter media contained therein. A support rib46 is formed beneath each port 40 to reinforce the port. Support rib 46also strengthens the fluid communication openings between the port 40and filter element dome 30 to prevent tearing of the port 40 from thedome region 30.

As will be discussed in greater detail below, each filter housingelement 20 or 22 is preferably injection molded from a flexiblethermoplastic material, such as flexible PVC material. The components ofeach element, including the flange 24, domed region 30, port 40 havingopening 42, conduit stop 44, and support rib 46 are integrally molded asa single, unitary component. Unlike prior art devices, there is aminimized risk of fluid leaking at the junction of domed portion 30 andport 40.

Various types of filter media can be contained within the interiorcavity 32. For example, a porous screen filter material, or a fibrousdepth filter material, in single layers or in a multiple layer stack,can be used. An example of a filter media that may be sealed within theinterior cavity 32 is best shown in FIG. 6. As shown, a membrane offilter media 60 having a periphery 62 is arranged and sealed betweenfilter housing elements 20 and 22. The preferred filter media 60 is asoft polyester membrane having a 250 micron mesh. However, it is to beunderstood that any filter media, including other types of filter mediamembranes, could be used in the present invention. The preferred mediais suitable for filtering particulate from red blood cells and plateletpoor plasma before it is returned to a blood donor.

In a preferred embodiment, filter membrane 60 is heat sealed between therespective flanges 24 of housing element 20 and housing element 22 toform the interior region 32. The interior region 32 can be furtherdivided into a first cavity 34 defined by housing element 20 and a firstside 62 of filter membrane 60 and a second cavity 36 defined by housingelement 22 and a second side 64 of filter membrane 60.

Again referring to FIG. 7, a fluid conduit 50 and 52, such as flexiblemedical grade plastic (e.g., PVC) or rubber tubing, can be attached toports 40 by conventional means such as an interference fit or with theaid of a solvent. In a preferred application, fluid flows throughopening 42 in port 40 formed in first or upper filter housing 20. Thefluid then flows into first interior cavity 34, through filter media 60and into second interior cavity 36. The fluid exits the filter assembly10 by flowing through the opening 42 formed in port 40 of filter housing22. The preferred embodiment of the filter assembly 10 depicts thelocation of the filter ports 40 at the top of the domed portion 30. Thepreferred embodiment 10 further depicts that the port 40 is formedsubstantially tangentially to the wall of the domed portion 30. The typeof fluid to be filtered, whether or not the filter assembly must trapair within its interior region and the physical constraints of thefilter application may dictate the orientation and location of port 40.It is to be understood that different locations and orientations of theport 40 may be made without deviating from the invention.

It is, thus, appreciated that the port 42 is formed in each filterhousing element 20 generally tangential or parallel to the wall of theelement. In the case of a filter assembly 10, the available surface areaof the filter media 60 is maximized since the filter membrane itselfextends to the periphery of the filter housing interior cavity 32without adversely affecting fluid flow in and out of the filterassembly.

As best illustrated in FIG. 7 at reference numeral 38, the filterassembly 10 of the present invention is flexible and thus capable ofcollapsing (as shown) and expanding depending upon the fluid orcombination of fluids flowing through the filter assembly. For example,if both a liquid, such as blood, and air are simultaneously flowingthrough a non-flexible or rigid filter assembly, a phenomenon known asfoaming is likely to occur. The present invention 10 prevents thisphenomenon by its ability to collapse when the volume of anon-compressible fluid (e.g. liquid) is decreased. Decreasing the volumeof the interior cavity 32 prevents the foaming phenomenon fromoccurring.

The present filter assembly 10 also functions to entrap air within itsinterior cavity 32. The design lends itself to filter applications onhorizontal planes such as the top panel of an instrument. By locatingthe inlet and outlet ports 42 in the central portion of each dome andprovided the filter assembly 10 is positioned in a horizontalorientation (as shown in FIG. 7), any air contained within the fluidbeing passed through the filter 10 is trapped within the interior cavity32. When the fluid enters the cavity 32 of the horizontally orientedfilter assembly, the air will remain in an upper portion of the cavity32 while the fluid will pass through the filter media 60 and toward theopposite or lower end of the cavity 32.

Although not specifically illustrated, it is within the province of theinvention to provide a single flexible filter element that is adhered toa filter media or a non-flexible filter member. A port may be integrallyformed in the filter element and a supply tube may be attached thereto.While different in structure, this alternative design would allow thefilter assembly to perform both the filtration function and airentrapment function discussed above.

The filter assembly 10 of the present invention is typically adisposable or single use item. Therefore, it is important that thefilter assembly 10 can be manufactured in an efficient and reliablemethod. Multiple filter housing elements 20 are preferablysimultaneously formed by an injection molding process as illustrated inFIGS. 8 and 9. The following description contemplates four filterhousing elements 20/22 being formed by an injection molding process andfour filter assemblies 10 being formed in a subsequent assembly process.It is to be understood that any number of filter housing elements andfilter assemblies could be formed at the same time without deviatingfrom the present invention.

Referring specifically to FIG. 9, thermoplastic material, such asflexible polyvinyl chloride, is injected between mating upper and lowerdie halves 70 and 72. When the die halves 70 and 72 are separated, asshown in FIG. 9, one or more filter housing elements 20/22 in the formof an integral strip 80 are ejected from the tooling. The strip of fourfilter housing elements, integrally connected by a web 80, is shown inFIGS. 8 and 9. As described supra, each filter housing element 20/22includes a flange portion 24, domed region 30 and port 40. In addition,a carrier web 74 extends from, and in some cases connects, filterhousing elements 20/22. Carrier web 74 may have one or more apertures 76formed therein.

A method of forming a filter assembly 10 of this invention is shown indetail in FIGS. 10-13. As seen in FIG. 10, a first strip 80 ofintegrally connected filter housings 20/22 is placed over a filtermembrane strip 82. The number of filter housings formed on strip 80 canbe any desired number. A second strip of filter housings 80 is placedbelow the filter membrane strip 82 as shown. Ideally, the number offilter housing in first strip should be same as the number of filterhousings in second strip. As best seen in FIG. 10, the orientation ofthe top filter housing element ports 40 is opposite the orientation ofthe bottom filter housing element ports 40. While this is the preferredarrangement of the housing element strips 80, the ports 40 could havethe same orientation.

The first strip 80, filter membrane 82 and second strip 80 are broughttogether as shown in FIG. 11 forming a pre-assembly 86. It is importantto note that the filter membrane strip is sufficiently narrow and doesnot cover the apertures 76 formed in the first and second strips 80. Itshould also be noted that the apertures 76 of the first strip 80 are inalignment with the apertures 76 of the second strip 80. This insuresthat the flange portions 24 of the respective filter housing elementsare in substantial alignment as well.

As seen in FIG. 12, a pair of opposed dies 90 and 92 are positioned onopposite sides of filter housing element strip, filter membrane, filterhousing element strip pre-assembly 86. Dies 90 and 92 are provided withaligned concave recesses 94 that form a pocket. While not shown, one ormore mandrels may be provided on the dies for receiving the apertures infilter housing element strips 80 and positively aligning the stripsprior to final assembly. Dies 90 and 92 are brought together for apredetermined amount of time. Preferably a stop is provided toaccurately space dies 90 and 92 apart from each other. RF energy is thensupplied through dies 90 and 92 in order to soften the thermoplasticmaterial of the mating filter housing elements flanges 24. Dies 90 and92, which remain relatively cool, act as a mold for the softenedmaterial. Material from the flange 24 of the first outer filter housingelement 20 flows through the filter membrane strip 82. Likewise,material from the flange 24 of second outer filter housing element 22flows through the filter membrane strip 82. The melted peripheryportions 24 of housing elements 20 and 22 serve to reinforce thejunction between housings 20 and 22 and the filter membrane strip 82. Adepression 38 of slightly decreased thickness is formed along theconjunctive periphery surrounding each filter assembly 10. After a briefperiod of cooling, the softened and flowing thermoplastic materialhardens sufficiently and dies 90 and 92 can be withdrawn.

RF energy is applied for the dielectric heating step through a mechanismwhich feeds the energy equally to each die halve. Preferably, amechanical stop is used to ensure that the two dies are separated by0.020 inch. Since the dies are not greatly heated by the dielectricheating, they can be withdrawn after a brief cooling period.

After the assembly is thus formed by the foregoing procedure, themultiple filter assemblies are die cut as shown in FIG. 13, intoindividual filter assemblies. First and second cutting dies 96 and 98,commonly known in the trade, having cutting edges 100, perform the diecutting operation. A strip of assembled filter assemblies is placedbetween the dies 96 and 98. Again while not shown, one or more mandrelsmay be positioned on the dies to properly align the multiple filterassembly prior to the cutting operation.

Finally, conduits 50 and 52 can be applied to the filter assembly 10 byany known method, for example, interference fit, adhesive or solventbonding.

Referring now to FIGS. 14 through 19, an alternative embodiment offilter assembly 10 can be seen to include first and second filterhousing elements 20 and 22. As will hereinafter be appreciated, and asis apparent from FIGS. 15 and 16, the housing elements 20 and 22 areidentical. Each housing element 20 and 22 includes a flange 24 formedabout its periphery 26. A substantially flat flexible region 31 isformed within the flange area 24. The filter housing elements 20 and 22are arranged, as will be described in greater detail, so that theirflexible regions 31 form and define an interior filter cavity 32.

The flexible region 31 of each filter housing element 20 or 22 has atleast one port 40 formed integral with the filter housing element. Port40 includes an inlet 42 that passes though flexible region 31 and thatis in fluid communication with the interior cavity 32 of the filterassembly 10. Inlet 42 is sized to receive the end of a fluid carryingconduit, such as a flexible medical grade plastic (e.g., PVC) or rubbertube or hose. As best shown in FIG. 17, a shoulder 44 is formed withineach inlet 42 to act as a conduit stop. The conduit stop prevents theinsertion of a conduit too far into the filter assembly thereby possiblydamaging or rupturing the filter media contained therein.

Each filter housing element 20 or 22 is preferably injection molded froma flexible thermoplastic material, such as flexible PVC material. Thecomponents of each element, including the flange 24, flexible region 31,port 40 having opening 42, and conduit stop 44 are integrally molded asa single, unitary component. Unlike prior art devices, there is aminimized risk of fluid leaking at the junction of flexible portion 31and port 40.

An example of a filtration medium that may be sealed within the interiorcavity 32 is best shown in FIG. 19. As shown, a filtration medium 61having a periphery 62 is arranged and sealed between filter housingelements 20 and 22. The filtration medium may include polyester mesh,cotton wool, cellulose acetate or another synthetic fiber likepolyester.

In a preferred alternative embodiment, filter membrane 61 is heat sealedbetween the respective flanges 24 of housing element 20 and housingelement 22 to form the interior region 32. The interior region 32 can befurther divided into a first half 35 defined by housing element 20 and afirst side 62 of filter membrane 61 and a second half 37 defined byhousing element 22 and a second side 64 of filter membrane 61. It is tobe understood that the filtration medium need not be sealed within theperiphery of the filter device, but may simply be located within theinterior region 32.

In use a fluid, such as whole blood, flows through opening 42 in port 40formed in first or upper filter housing 20. The fluid then flows intofirst half 35, through filter media 61 and into second half 37. Thefluid exits the filter assembly 10 by flowing through the opening 42formed in port 40 of filter housing 22. The depicted alternativeembodiment of the filter assembly 10 shows the location of each filterports 40 is formed substantially tangentially to the wall of theflexible portion 31. The type of fluid to be filtered, whether or notthe filter assembly must trap air within its interior region and thephysical constraints of the filter application may dictate theorientation and location of port 40. It is to be understood thatdifferent locations and orientations of the port 40 may be made withoutdeviating from the invention.

It is, thus, appreciated that the port 42 is formed in each filterhousing element 20 generally tangential or parallel to the wall of theelement. In the case of a filter device 10, the available surface areaof the filtration medium 61 is maximized since the filter membraneitself extends to or near the periphery of the filter housing interiorcavity 32 without adversely affecting fluid flow in and out of thefilter assembly.

The filter assembly 10 of this alternative embodiment is also flexibleand thus capable of collapsing and expanding depending upon the fluid orcombination of fluids flowing through the filter assembly. For example,if both a liquid, such as blood, and air are simultaneously flowingthrough a non-flexible or rigid filter assembly, a phenomenon known asfoaming is likely to occur. The present invention 10 prevents thisphenomenon by its ability to collapse when the volume of anon-compressible fluid (e.g. liquid) is decreased. Decreasing the volumeof the interior cavity 32 prevents the foaming phenomenon fromoccurring.

It is preferred that the outer filter housings 20 and 22 be injectionmolded of flexible PVC material which is selected because of itsreceptiveness to dielectric heat sealing. Any suitable material can bemodified by addition of various plasticizers and readily sterilizedusing conventional sterilization methods.

In a preferred example of the invention, filter housing elements 20/22are injection molded from flexible polyvinyl chloride. The injectionmolding dies provide for a uniform wall thickness of 0.020 inches.

The present invention 10 may also be utilized in manual blood collectionassemblies for removing undesirable materials, e.g., leukocytes, fromred blood cells, platelet-rich plasma, platelet-poor plasma, or plateletconcentrate. A description of representative blood collection assembliesis set forth below.

One representative blood collection assembly 100 for removingundesirable materials, e.g., leukocytes, from red blood cells is shownin FIG. 20. The assembly 100 comprises a closed manual blood collectionsystem. In the illustrated embodiment, the assembly 100 serves toseparate and store the red blood cells as well as the plasma andplatelet blood components by conventional centrifugation techniques,while removing undesired matter from the red blood cells prior tostorage. In the illustrated embodiment, the undesired matter is removedgenerally by filtration and specifically utilizing the filter devicedescribed herein.

In the illustrated system shown in FIG. 20, the assembly 100 includes aprimary bag or container 116 and various transfer bags or containers118, 126, and 134 that are attached to the primary bag 16 by integrallyattached branched tubing 128. The tubing 128 is divided by appropriateconnectors into branches 129, 130, and 132.

In the illustrated embodiment, flow control devices 131, 133, and 135are provide on the branched fluid flow paths as shown to enabledirecting of the fluid transfers in a desired sequence of steps. In theillustrated arrangement, the flow control devices take the form ofconventional roller clamps that are manually operated to open and closethe associated tubing paths.

In use, the primary bag 116 (which is also called a donor bag) receiveswhole blood from a donor through integrally attached donor tubing 122that carries an phlebotomy needle 124. A suitable anticoagulant A iscontained in the primary bag 116.

The transfer bag 126 contains a suitable storage solution S for the redblood cells. One such solution is disclosed in Grode et al U.S. Pat. No.4,267,269. Another solution is sold under the brand name ADSOL®.

The transfer bag 118 is intended to receive the platelet and plasmablood components associated with the whole blood collected in theprimary bag 116. The transfer bag 118 ultimately serves as the storagecontainer for the platelet concentrate constituent. The transfer bag 126also ultimately serves as the storage container for the platelet-poorplasma constituent.

Flow control device 133 is located in tubing 130 to control fluid flowto and from the transfer bag 118. Flow control device 135 is located intubing 132 to control fluid flow to and from transfer bag 126.

Tubing 128 and 129 form a flow path to the container 134. This flow pathincludes the filter device 10 of the present invention for separatingundesired matter from blood cells. Flow control means 131 is located ontubing 129 that leads to the filter 10. The container 134 ultimatelyserves as a storage container for the red blood cells after passagethrough the filter device 10.

The bags and tubing associated with the processing assembly 100 can bemade from conventional approved medical grade plastic materials, such aspolyvinyl chloride plasticized with di-2-ethylhexyl-phthalate (DEHP).The ends of the tubing may be connected by “Y” or “T” connectors to formthe branched fluid flow paths.

Alternatively, transfer container 118, which is intended to store theplatelet concentrate, can be made of polyolefin material (as disclosedin Gajewski et al U.S. Pat. No. 4,140,162) or a polyvinyl chloridematerial plasticized with tri-2-ethylhexyl trimellitate (TEHTH). Thesematerials, when compared to DEHP-plasticized polyvinyl chloridematerials, have greater gas permeability that is beneficial for plateletstorage.

The blood collection and storage assembly 100, once sterilized,constitutes a sterile, “closed” system, as judged by the applicablestandards in the United States.

When the system 100 is used, whole blood is collected in the primary bag116. The collected whole blood is centrifugally separaed within theprimary bag 116 into a red blood cell component (designated RBC in FIG.21) and platelet-rich plasma component (designated PRP in FIG. 21).During such separation techniques, a layer of leukocytes (commonlycalled the “buffy coat” and designated BC in FIG. 21) forms between thered blood cells and the platelet-rich plasma.

In a first processing mode (shown in FIG. 21), the platelet-rich plasmacomponent is transferred by conventional techniques from the primary bag116 to the transfer bag 118. This transfer is accomplished by openingclamp 133, while closing clamps 131 and 135. In this step, attempts aremade to keep as many leukocytes in the primary bag 116 as possible. Thetransfer of platelet-rich plasma into the first transfer bag 118 leavesthe red blood cells and the remaining leukocytes behind in the primarybag 116.

In a second processing mode (shown in FIG. 22), the solution S istransferred from the transfer bag 126 into the primary bag 116. Thistransfer is accomplished by closing clamps 131 and 133, while openingclamp 135.

In a third processing mode (shown in FIG. 23), the mixture of additivesolution S and the red blood and leukocytes in the primary bag 116 istransferred into the transfer bag 134 through the filter device 10. Thistransfer is accomplished by closing the clamps 133, 135 and 155 whileopening the clamp 131. The red blood cells and additive solution S enterthe container 134 essentially free of leukocytes.

It should be appreciated that the filtration medium within the filterdevice housing 20/22 can be used to remove all types of undesiredmaterials from different types blood cells, depending upon itsparticular construction. In the illustrated embodiment, the filterdevice 10 is intended to remove leukocytes from the red blood cellsprior to storage. For example, the filtration medium 60 located withinhousing 20/22 can include cotton wool, cellulose acetate or anothersynthetic fiber like polyester. The undesired matter is removed from thered blood cells by the filter device 10.

In a fourth processing mode (shown in FIGS. 23 and 24), a constituent ofthe component contained in the transfer bag 118 is transferred to thetransfer bag 126. In the illustrated embodiment, this processing mode isaccomplished by first separating the transfer bags 118 and 126 from thesystem 100 (as FIG. 23 shows). The separation of the bags isaccomplished by forming snap-apart seals in the tubing 130 that makes upthe branched fluid flow path 130 leading to the transfer bags 118 and126. A conventional heat sealing device (for example, the Hematron®dielectric sealer sold by Baxter Healthcare Corporation) can be used forthis purpose. This device forms a hermetic, snap-apart seal in thetubing 130 (this seal is schematically shown by an “x” in FIGS. 23 and24). Preferably, the donor tubing 122 is also sealed and disconnected inthe same fashion (as shown in FIG. 23).

Once separated, the platelet-rich plasma undergoes subsequentcentrifugal separation within the transfer bag 118 into plateletconcentrate (designated PC in FIGS. 23 and 24) and platelet-poor plasma(designated PPP in FIGS. 23 and 24). The platelet-poor plasma istransferred into the transfer bag 126 (by opening the clamps 133 and135), leaving the platelet concentrate in the first transfer bag 118.

As FIG. 24 shows, the bags 118 and 126 are then themselves separated byforming snap-apart seals “x” in the tubing 130 for subsequent storage ofthe collected components. The transfer bag 134 (containing the filteredred blood cells) is also separated in the same fashion for storage (asFIG. 24 also shows).

Should air become trapped in the transfer bag 134, it may be necessaryto transfer the air through path 128 into the primary bag 116 beforeseparating the transfer bag 134 from the system 100. As seen in FIGS.20-24, an air bleed channel 154 can be incorporated on either side ofthe filter device 10 for this purpose. Means such as a clamp 155 can beprovided to open and close bypass line 154 as required. Clamp 131 isopened during this step to allow the vented air to proceed into theprimary bag 116. To alternatively prevent flow of the blood cells beingfiltered through this channel in the filtration step, a suitable one-wayvalve (not shown) may be provided within the filter device 10 to closethe end of the channel near the inflow opening to filter device 10.

In an optional fifth processing mode and now referring to FIG. 25, theplatelet concentrate remaining in first transfer bag 118 may be filteredthrough a separate filter device 10 to remove leukocytes and yieldfiltered platelet concentrate (designated FPC in FIG. 25). A fifthtransfer bag 170 is attached to transfer bag 118 by tubing 172. Tubing172 forms a flow path from transfer bag 118 to transfer bag 170. Theflow path includes a separate or second inline filter device 10 forseparating the undesired matter from the platelet concentrate. Ifdesired a flow control device, such as a roller clamp (not shown), maybe provided on the tubing 172. The transfer bag 170 ultimately serves astorage container for the filtered platelet concentrate after passagethrough the filter device 10.

In the embodiment shown in FIG. 26, the system 100 comprises threeinitially separate subassemblies 160, 162 and 164. The subassembly 160constitutes a blood collection assembly and includes the primary bag 116and integrally joined tubing 128. The subassembly 162 constitutes afirst transfer assembly and includes the transfer bags 118 and 126 withintegrally joined tubing 130 and 132 (with associated roller clamps 133and 135). The subassembly 164 constitutes a second transfer assembly andincludes the transfer bag 134, the filter device 10, and the tubing 129(with associated roller clamp 131).

The separate subassemblies 160, 162, and 164 are joined together at timeof use to comprise the system 100 shown in FIG. 20. For this purpose,the embodiment shown in FIG. 26 includes a means for connecting theinitially separate subassemblies 160, 162, and 164 together. Theconnection means is associated with each of the initially separatesubassemblies 160, 162, and 164.

In the embodiment shown in FIG. 26, the connection means comprisesmating sterile connection devices (designated 166 a, 166 b, 166 c and166 d). The devices 166 a, 166 b, 166 c, and 166 d are described inGranzow et al U.S. Pat. Nos. 4,157,723 and 4,265,280, which areincorporated herein by reference.

The tubing 128 of the subassembly 160 carries the devices 166 a and 166d. The tubing 130 of the transfer subassembly 162 carries the device 166b. The tubing 129 of the transfer subassembly 164 carries the device 166c.

The devices 166 a, 166 b, 166 c, and 166 d normally close the associatedassemblies 160, 162, and 164 from communication with the atmosphere andare opened in conjunction with an active sterilization step which servesto sterilize the regions adjacent to the interconnecting fluid path asthe fluid path is being formed. These devices 166 a, 166 b, 166 c, and166 d also hermetically seal the interconnecting fluid path at the timeit is formed. The use of these sterile connection devices 166 a, 166 b,166 c, and 166 d assures a probability of non-sterility that exceeds onein a million. The devices 166 a, 166 b, 166 c, and 166 d thus serve toconnect the subassemblies 160, 162, and 164 without compromising theirsterile integrity.

Alternately, the connection means can comprise the sterile connectingsystem disclosed in Spencer U.S. Pat. No. 4,412,835 (not shown). In thisarrangement, this system forms a molten seal between the tubing ends.Once cooled, a sterile weld is formed.

The subassemblies 160, 162, and 164, once sterilized, each constitutes asterile, “closed” system, as judged by the applicable standards in theUnited States.

A blood collection system 200 for removing undesirable material, e.g.,leukocytes, from whole blood prior to centrifugal processing is shown inFIG. 27. Again, the assembly comprises a closed blood collection system.In the illustrated embodiment, the assembly 200 serves to separate andstore red blood cells as well as plasma or plasma-platelet bloodcomponents by conventional centrifugation techniques, while removingundesirable material such as leukocytes prior to storage. In theillustrated embodiment, the undesired matter is removed generally byfiltration and specifically utilizing the filter device 10 describedherein.

In the illustrated embodiment shown in FIG. 27, the assembly 200includes a primary bag or container 216 and various transfer bags orcontainers 218, 226, and 234. Transfer bag 234 is attached to theprimary bag 216 by integrally attached tubing 228. Transfer bags 218 and234 are attached to transfer bag 234 by integrally attached tubing 229.The tubing 229 is divided by appropriate connectors into branches 230and 232.

In the illustrated embodiment, flow control devices 231, 233, and 235are provided on the branched fluid flow paths as shown to enabledirecting of the fluid transfers in a desired sequence of steps. In theillustrated arrangement, the flow control devices take the form ofconventional roller clamps that are manually operated to open and closethe associated tubing paths.

In use, the primary bag 216 (which is also called a donor bag) receiveswhole blood from a donor through integrally attached donor tubing 222that carries an phlebotomy needle 224. A suitable anticoagulant A iscontained in the primary bag 216.

The transfer bag 226 contains a suitable storage solution S for the redblood cells. One such solution is disclosed in Grode et al U.S. Pat. No.4,267,269. Another solution is sold under the brand name ADSOL®.

The transfer bag 218 is intended to receive the plasma componentsassociated with the whole blood collected in the primary bag 216. Theplasma component may also contain platelets and comprise platelet-richplasma, if the media in the filter device 10 has the characteristic ofallowing platelets to pass. Otherwise, the plasma component comprisesplatelet-poor plasma. The transfer bag 218 ultimately serves as thestorage container for the platelet constitent contained in the plasmaconstituent. In this arrangement, the transfer bag 226 also ultimatelyserves as a storage container for the plasma constituent. The transferbag 234 also ultimately serves as the storage container for the redblood cell constituent.

Flow control device 233 is located in tubing 230 to control fluid flowto and from the transfer bag 218. Flow control device 235 is located intubing 232 to control fluid flow to and from transfer bag 226.

Tubing 228 forms a flow path from donor bag 216 to the container 234.This flow path includes the filter device 10 of the present inventionfor separating undesired matter such as leukocytes from the whole bloodcollected in the primary bag 216. Flow control means 231 is located ontubing 228 that leads to the filter 10.

The bags and tubing associated with the processing assembly 200 can bemade from conventional approved medical grade plastic materials, such aspolyvinyl chloride plasticized with di-2-ethylhexyl-phthalate (DEHP).The ends of the tubing may be connected by “Y” or “T” connectors to formthe branched fluid flow paths.

Alternatively, transfer container 218, which is intended to store theplatelet constitent, can be made of polyolefin material (as disclosed inGajewski et al U.S. Pat. No. 4,140,162) or a polyvinyl chloride materialplasticized with tri-2-ethylhexyl trimel-litate (TEHTH). Thesematerials, when compared to DEHP-plasticized polyvinyl chloridematerials, have greater gas permeability that is beneficial for plateletstorage.

It should be appreciated that the filtration medium within the filterdevice housing 20/22 can be used to remove all types of undesiredmaterials from different types blood cells, depending upon itsparticular construction. In the illustrated embodiment, the filterdevice 10 is intended to remove leukocytes from whole blood cells priorto centrifugation in the transfer bag 234. The media of the filterdevice 10 may also remove platelets, if desired. For example, thefiltration medium 60 located within housing 20/22 can include polyestermesh, cotton wool, cellulose acetate or another synthetic fiber likepolyester.

After filtration, the bags 216 and 234 are separated by formingsnap-apart seals “x” in the tubing 228. The separation of the bags isaccomplished by forming snap-apart seals in the tubing 228 that makes upthe branched fluid flow paths leading to the transfer bags. Aconventional heat sealing device (for example, the Hematron® dielectricsealer sold by Baxter Healthcare Corporation) can be used for thispurpose. This device forms a hermetic, snap-apart seal in the tubing(this seal is schematically shown by an “x” in FIG. 28).

In a first processing mode (shown in FIG. 28), the filtered whole bloodwithin the transfer bag 234 is centrifugally separated within thetransfer bag 234 into a red blood cell component (designated RBC in FIG.28) and a plasma constituent, which, in the illustrated embodiment, isplatelet-rich plasma component (designated PRP in FIG. 28).

The platelet-rich plasma component is transferred by conventionaltechniques from the transfer bag 234 to the transfer bag 218. Thistransfer is accomplished by opening clamp 233, while closing clamp 235.The transfer of platelet-rich plasma into the transfer bag 218 leavesthe red blood cells behind in the transfer bag 234.

In a second processing mode (shown in FIG. 29), the solution S istransferred from the transfer bag 226 into the transfer bag 234. Thistransfer is accomplished by closing clamp 233, while opening clamp 235.

In a third processing mode (not shown), the red blood cells may betransferred by conventional techniques from the transfer bag 234 to thetransfer bag 226 for storage. This transfer is accomplished by openingclamp 235, while closing clamp 233. However, in the illustratedembodiment (shown in FIG. 30), where platelet concentrate is desired,the red blood cells and storage solution are left in the transfer bag234 for storage, leaving the transfer bag 226 open to receiveplatelet-poor plasma constituent in the course of subsequent processing.

In this arrangement, as FIG. 31 shows, the bags, 218 and 226 are thenthemselves separated from the bag 234 by forming snap-apart seals “x” inthe tubing 229. The separated bags 218 and 226 are then placed in acentrifuge to separate the platelet-rich plasma in the bag 218 intoplatelet concentrate and platelet-poor plasma. The platelet poor plasmais expressed from the bag 218 into the bag 226, leaving the plateletconcentrate in the bag 218 for long term storage.

Other modifications of the invention within the ability of those skilledin the art can be made without departing from the true scope of theappended claims.

What is claimed is:
 1. A filter device comprising: first and secondflexible housing elements, each made from a thermoplastic material, amolded inlet port carried by the first flexible housing element, amolded outlet port carried by the second flexible housing element, afilter medium located between the first and second flexible housingelements, and a peripheral seal formed by application of radio frequencyheating and pressure to join the first and second flexible housingelements directly to the filter medium and encapsulate the filter mediumbetween the first and second flexible housing elements.
 2. A filterdevice according to claim 1 wherein the inlet port is carried by thefirst flexible housing element spaced from the peripheral seal, andwherein the outlet port is carried by the second flexible housingelement spaced from the peripheral seal.
 3. A blood collection systemcomprising a container for holding blood, a blood filter device asdefined in claim 1 or 2, and tubing connecting the blood filter deviceto the container.